Size effects in barium titanate thin film heterostructures with conductive oxide electrodes

Thin film, small particle, and fine grained materials have long been known to behave differently from their bulk counterparts, and as such, these differences have been termed size effects. The origins of size effects, though well known for some materials, in ferroelectrics are largely misunderstood. Currently inhibiting the application of ferroelectrics, these effects become commercially important in devices such as MEM's, MLC's, and DRAM's. Included in such structures are ferroelectric layers with thicknesses or grains approaching the critical size below which ferroelectric properties degrade. Epitaxial BaTiO₃ thin film heterostructures utilizing conductive oxide electrodes have been deposited by PLD, while 4-circle x-ray diffraction, electrical property measurements, and RBS have been applied to characterize the films. The Curie temperatures for BaTiO₃ films were found to be depressed by as much as 150 °C, with the magnitude of this depression believed to be dependent upon the coherent crystal size of the films.